Sodium trimetaphosphate in combination with a potassium hydroxide base has been described as a useful builder in homogeneous automatic dishwashing compositions. See U.S. Pat. No. 5,213,706 issued to Rapisarda et al. on May 25, 1993. The combination of this builder with a potassium hydroxide base avoids the use of additional potassium salts to solubilize the alkaline components of the compositions and further avoids the undesirable reaction of other bases with the metaphosphate anion.
When sodium trimetaphosphate is combined with potassium hydroxide, the builder is hydrolyzed in situ to form a soluble sodium/potassium tripolyphosphate (SKTP) having the following formula: EQU (NaPO.sub.3).sub.3 +2KOH=Na.sub.3 K.sub.2 P.sub.3 O.sub.10 +H.sub.2 O
It was subsequently discovered that detergent compositions containing SKTP exhibited precipitation of tripolyphosphate salts causing spotting on machine and dishware surfaces. The precipitate problem is especially pronounced when the detergent compositions do not contain an alkali silicate and are formulated at a pH of below about 10.